Remove RM pool configuration and yarn_pool query option/profile property

Admission control adds support for configuring pools via a fair scheduler
allocation configuration, so the pool configuration mechanism is no longer
needed. This also renames the "yarn_pool" query option to the more general
"request_pool" as it can also be used to configure the admission controller
when RM/Yarn is not used. Similarly, the query profile shows the pool as
"Request Pool" rather than "Yarn Pool".

Change-Id: Id2cefb77ccec000e8df954532399d27eb18a2309
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1668
Reviewed-by: Matthew Jacobs <mj@cloudera.com>
Tested-by: Matthew Jacobs <mj@cloudera.com>
Tested-by: jenkins
Admission control tests: Increase thread join timeout and remove unnecessary locking

In some rare cases on overloaded machines, the thread join timeout of 10 seconds isn't
long enough. Also, taking the lock at that time isn't necessary because the main thread
will not attempt to cancel a thread unless it is already in the list of running threads.
Threads are added to that list only after they submit their query.

Change-Id: I23a67d726bc25221f0e9331ca1a3e9f5363f821d
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1744
Reviewed-by: Matthew Jacobs <mj@cloudera.com>
Tested-by: Matthew Jacobs <mj@cloudera.com>
Tested-by: jenkins
IMPALA-759: Parquet writer: all NULL columns should use PLAIN encoding.

Change-Id: I35d5997d7623239f6cfce7f97a5802545126ea4c
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1750
Reviewed-by: Marcel Kornacker <marcel@cloudera.com>
Tested-by: jenkins
IMPALA-816: Fix JDBC getFunctions API.

Change-Id: I452306be05363cfb1502dd6a2f82cdf84dfad35b
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1749
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins